Compression Ratio help. - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

Lsguy · 05-22-2021, 01:48 AM

So I picked my motor up from the machine shop yesterday and the work done is great but I do have a problem. Its a gen 4 6.0 stroked to 408.
Bore 4.030
Stroke 6.125
Pistons wis k464x3
Dome 3.00
Heads stock ls3 duel 660 springs
CnC Deck 9.230

I was told with a 55mm gasket compression would be 11.1 from what I've read thats way to high for pump gas so what can I do without ordering some more $900 pistons. Its a Turbo car

ttshovel · 05-22-2021, 02:22 AM

Aside from ordering pistons your only real option is to go to e85. You can run a thicker gasket but thats asking a lot. The math works out to 11.04:1 with a ls9 headgasket(.059 thick) and assuming zero deck.

Lsguy · 05-22-2021, 03:54 AM

Quote:

Originally Posted by ttshovel

Aside from ordering pistons your only real option is to go to e85. You can run a thicker gasket but thats asking a lot. The math works out to 11.04:1 with a ls9 headgasket(.059 thick) and assuming zero deck.

The only problem with e85 is I live in knoxville tn and there's only 2 gas stations around here that has e85 and they're both 40 minutes from where I live on top of that it puts me out of doing any type of drag week or anything like that.

Lsguy · 05-22-2021, 04:20 AM

Quote:

Originally Posted by ttshovel

Aside from ordering pistons your only real option is to go to e85. You can run a thicker gasket but thats asking a lot. The math works out to 11.04:1 with a ls9 headgasket(.059 thick) and assuming zero deck.

Would it be possible to get the CR down by swapping to a aftermarket head

ttshovel · 05-22-2021, 04:35 AM

Quote:

Originally Posted by Lsguy

Would it be possible to get the CR down by swapping to a aftermarket head

You could get it down with an aftermarket head, but even so a .059 ls9 gasket with a 72cc chamber would net 10.59:1

They do have a .070 gasket that gets you 10.34:1 with a 72cc head.

G8One2 · 05-23-2021, 07:39 AM

Static compression means nothing. Your cam and valve events dictate your effective compression. My last car (g8) had a 6.0L , .035" gaskets and 11.7 compression that ran just fine with no knock on 93 octane. Your best bet would be to go with the shop who built it, recommendation.

Rem0v3r · 05-23-2021, 09:22 AM

I second going to e85.. youre a big cube boosted ls car.. at some point you're going to have to transition to E if you want to make good power... go buy a bunch of gas cans and fill up once a month.. at any rate, going to get gas is a good excuse to drive your car :-)

ttshovel · 05-23-2021, 10:52 AM

Quote:

Originally Posted by G8One2

Static compression means nothing. Your cam and valve events dictate your effective compression. My last car (g8) had a 6.0L , .035" gaskets and 11.7 compression that ran just fine with no knock on 93 octane. Your best bet would be to go with the shop who built it, recommendation.

Hes not gonna get dynamic compression down enough with a cam being boosted. You must have missed that last line of his first post

gunchamp · 05-23-2021, 11:54 AM

Quote:

Originally Posted by Lsguy

So I picked my motor up from the machine shop yesterday and the work done is great but I do have a problem. Its a gen 4 6.0 stroked to 408.
Bore 4.030
Stroke 6.125
Pistons wis k464x3
Dome 3.00
Heads stock ls3 duel 660 springs
CnC Deck 9.230

I was told with a 55mm gasket compression would be 11.1 from what I've read thats way to high for pump gas so what can I do without ordering some more $900 pistons. Its a Turbo car

Depends on how much boost. Im running 11:1 with 10#s. Get a good tuner and it will be fine. Im running 93 octane. Seeing no issues with knock or anything and it pulls like a freight train

Lsguy · 05-26-2021, 11:54 PM

Thanks for the help... I do plan on keeping the Boost low when on pump gas and at the track the car will be on methanol. Sorry that's a newbie mistake I did not give enough info I was at work when I made that post.
I have put together a few cars before but mostly 2JZ stuff and it was all bolt ons. This is my first actual build.
I started this build with the intention to get my son into building cars and also to be able to upgrade later on to a aftermarket head and be able to make more power.

I got a question about lifters I ordered a set of Johnson 2116lsr three weeks later they're still not here when I called them they told me a good alternative was the morel 5290 I know that is not a short travel slow leak down lifter I don't think the 5290s will support the RPM in the future. Has anyone had any experience with those and what RPM are you turning them to

stevieturbo · 05-27-2021, 03:20 PM

Was CR not discussed with the builder before you got to this stage ?

AGP Turbo · 05-27-2021, 05:34 PM

It will only cost you a few hundred dollars to change the pistons out to the right -15or20cc and sell your flat tops at a bit of a loss. Otherwise on pump gas you are going to be limited to roughly 10psi and that's a total waste of all the money you've invested. 150+whp more available on pump gas by going lower compression.

Lsguy · 05-27-2021, 05:56 PM

Yes compression ratio was discussed. I'm not to concerned with Boost on pump gas my concern was would I be able to drive it at all on pump gas. I do plan to race it at the track so it will be on methanol when under high boost. Like I said I want to do some drag week type events and I live right outside of Sevierville Tennessee so take it to the rod runs. If I could run
10 pounds of boost are less on the street that would be fine. Could I set it up to spray meth like a water methanol kit when on pump gas to keep it happy.

ttshovel · 05-27-2021, 05:58 PM

You might wanna do your research on what it takes to run methanol as your primary fuel. It's not as easy as you'd think. You'll need a 10gpm fuel pump minimum

05-22-2021, 01:48 AM	#1
Lsguy Drives: 2010 camaro Join Date: Mar 2020 Location: Maryville TN Posts: 49	Compression Ratio help. So I picked my motor up from the machine shop yesterday and the work done is great but I do have a problem. Its a gen 4 6.0 stroked to 408. Bore 4.030 Stroke 6.125 Pistons wis k464x3 Dome 3.00 Heads stock ls3 duel 660 springs CnC Deck 9.230 I was told with a 55mm gasket compression would be 11.1 from what I've read thats way to high for pump gas so what can I do without ordering some more $900 pistons. Its a Turbo car Last edited by Lsguy; 05-22-2021 at 01:50 AM. Reason: forgot something

05-22-2021, 02:22 AM	#2
ttshovel Drives: 12 camaro ss, 72 chevelle, 91camaro Join Date: Dec 2013 Location: findlay,oh Posts: 2,070	Aside from ordering pistons your only real option is to go to e85. You can run a thicker gasket but thats asking a lot. The math works out to 11.04:1 with a ls9 headgasket(.059 thick) and assuming zero deck. __________________ 12 camaro ss 427lsx, th400, f310 heads, crower shaft mounts, gpi specd solid roller, shearerfab 2k hp a/w, twin bullseye 88mm turbos, hughes pro ssx bolt together converter, holley dominator, 8.50 cert, backhalf, Ford 9", 33x17x16 tires, c16 fuel

05-27-2021, 05:58 PM	#14
ttshovel Drives: 12 camaro ss, 72 chevelle, 91camaro Join Date: Dec 2013 Location: findlay,oh Posts: 2,070	You might wanna do your research on what it takes to run methanol as your primary fuel. It's not as easy as you'd think. You'll need a 10gpm fuel pump minimum __________________ 12 camaro ss 427lsx, th400, f310 heads, crower shaft mounts, gpi specd solid roller, shearerfab 2k hp a/w, twin bullseye 88mm turbos, hughes pro ssx bolt together converter, holley dominator, 8.50 cert, backhalf, Ford 9", 33x17x16 tires, c16 fuel

05-23-2021, 07:39 AM	#6
G8One2 Drives: 2014 Camaro 2SS Join Date: Feb 2015 Location: Metro Detroit Posts: 492	Static compression means nothing. Your cam and valve events dictate your effective compression. My last car (g8) had a 6.0L , .035" gaskets and 11.7 compression that ran just fine with no knock on 93 octane. Your best bet would be to go with the shop who built it, recommendation.

05-23-2021, 09:22 AM	#7
Rem0v3r Drives: 2013 ss2 vert l99 Join Date: Apr 2017 Location: South florida Posts: 151	I second going to e85.. youre a big cube boosted ls car.. at some point you're going to have to transition to E if you want to make good power... go buy a bunch of gas cans and fill up once a month.. at any rate, going to get gas is a good excuse to drive your car :-)

05-26-2021, 11:54 PM	#10
Lsguy Drives: 2010 camaro Join Date: Mar 2020 Location: Maryville TN Posts: 49	Thanks for the help... I do plan on keeping the Boost low when on pump gas and at the track the car will be on methanol. Sorry that's a newbie mistake I did not give enough info I was at work when I made that post. I have put together a few cars before but mostly 2JZ stuff and it was all bolt ons. This is my first actual build. I started this build with the intention to get my son into building cars and also to be able to upgrade later on to a aftermarket head and be able to make more power. I got a question about lifters I ordered a set of Johnson 2116lsr three weeks later they're still not here when I called them they told me a good alternative was the morel 5290 I know that is not a short travel slow leak down lifter I don't think the 5290s will support the RPM in the future. Has anyone had any experience with those and what RPM are you turning them to

05-27-2021, 03:20 PM	#11
stevieturbo Drives: it changes Join Date: Nov 2010 Location: Norn Iron Posts: 1,128	Was CR not discussed with the builder before you got to this stage ?

05-27-2021, 05:34 PM	#12
AGP Turbo Drives: All things Turbocharged Join Date: Dec 2010 Location: AZ Posts: 1,199	It will only cost you a few hundred dollars to change the pistons out to the right -15or20cc and sell your flat tops at a bit of a loss. Otherwise on pump gas you are going to be limited to roughly 10psi and that's a total waste of all the money you've invested. 150+whp more available on pump gas by going lower compression.

05-27-2021, 05:56 PM	#13
Lsguy Drives: 2010 camaro Join Date: Mar 2020 Location: Maryville TN Posts: 49	Yes compression ratio was discussed. I'm not to concerned with Boost on pump gas my concern was would I be able to drive it at all on pump gas. I do plan to race it at the track so it will be on methanol when under high boost. Like I said I want to do some drag week type events and I live right outside of Sevierville Tennessee so take it to the rod runs. If I could run 10 pounds of boost are less on the street that would be fine. Could I set it up to spray meth like a water methanol kit when on pump gas to keep it happy.